1. Field of the Invention
This invention relates in general to the manufacture of magnetic heads, and more particularly to a method for fabricating a non-electroplated metal shield using combination patterning and devices formed thereby.
2. Description of Related Art
Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modem personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.
As disk drive technology progresses, more data is compressed into smaller areas. Increasing data density is dependent upon read/write heads fabricated with smaller geometries capable of magnetizing or sensing the magnetization of correspondingly smaller areas on the magnetic disk. The advance in magnetic head technology has led to heads fabricated using processes similar to those used in the manufacture of semiconductor devices.
A typical disk drive is comprised of a magnetic recording medium in the form of a disk for storing information, and a magnetic read/write head for reading or writing information on the disk. The disk rotates on a spindle controlled by a drive motor and the magnetic read/write head is attached to a slider supported above the disk by an actuator arm. When the disk rotates at high speed a cushion of moving air is formed lifting the air bearing surface (ABS) of the magnetic read/write head above the surface of the disk.
The write portion of a read/write head is typically fabricated using a coil embedded in an insulator between a top and bottom magnetic layer. The magnetic layers are arranged as a magnetic circuit, with pole tips forming a magnetic gap at the air bearing surface of the head. When a data bit is to be written to the disk, the disk drive circuitry sends current through the coil creating a magnetic flux. The magnetic layers provide a path for the flux and a magnetic field generated at the pole tips magnetizes a small portion of the magnetic disk, thereby storing a data bit on the disk.
The read portion of the head is typically formed using a magnetoresistive (MR) element. This element is a layered structure with one or more layers of material exhibiting the magnetoresistive effect. The resistance of a magnetoresistive element changes when the element is in the presence of a magnetic field. Data bits are stored on the disk as small, magnetized region on the disk. As the disk passes by beneath the surface of the magnetoresistive material in the read head, the resistance of the material changes and this change is sensed by the disk drive control circuitry.
Typically, read head portions include shields, insulating layers and the above-mentioned magnetoresistive sensing layers. Shield layers have historically been fabricated using electroplated NiFe. However, other metals are needed for shield layers, and some of these other metals must be deposited by means other than electroplating. For example, the properties of some vacuum-deposited metals such as cobalt-zirconium-tantalum (CZT) make them attractive candidates for shield layers. However, the fabrication of a non-electroplated shield using typical processes presents problems due to the thickness of the material required. For example, if a relatively thick layer of metal is deposited full-film and then a patterning photo layer is applied to perform an ion mill to remove the metal from areas where the metal is not to be maintained, considerable overmill is required to clear the small features of the shield, i.e., the reader vias. This overmill would damage the underlying alumina layers below, and potentially damage the sensor buried under that alumina as well.
Alternatively, if a relatively thick layer of metal is deposited and then a photo layer is applied to perform a wet-etch, considerable over-etch is required to clear the field across all areas of the wafer. This over-etch will damage or completely remove small features that need to be retained in the final pattern such as reader vias, and potentially damage the underlying alumina or even the sensor. Moreover, a wet-etch process can have high etch variation across the water and from wafer to water, leaving some areas over-etched and others incompletely etched even on the same wafer.
A third alternative may be used wherein a resist layer is patterned with a release layer, the metal layer is deposited on top of the resist layer and then a liftoff procedure is performed to remove the metal from the field. However, the release layer must be of approximately equal thickness to the metal being patterned. This requires a relatively thick stack of patterning resist to be applied before metal deposition. This patterning resist can bubble and flow during the long metal deposition cycle. In experiments, even if the resist was thoroughly baked or “cured” before deposition, a clean deposit could not be achieved even on areas without resist. Further, small features would be obliterated by resist flow, and the bubbling can cause metal to flake off the wafer and contaminate the tool. Still further, putting resist in the metal deposition tools could cause magnetic degradation of all other materials deposited in the same chamber at a later date.
It can be seen then that there is a need for a process for fabricating a magnetic head shield compatible with using materials other than NiFe.